1. Field of the Invention
The present invention is related to compositions and methods for aging of beverages, particularly liquids to be aged in the presence of wood, and more particularly to the accelerated aging of distilled beverages.
2. Description of Related Art
Ethanolic distillates aged in wooden containers exhibit myriad chemical changes over the course of several years. These changes are believed to be due to three types of chemical reactions: 1) reactions involving only the distillate components, 2) extraction of wood-derived compounds that are soluble in the distillate, and 3) reactions of the distillate components with the extracted wood compounds (Liebmann and Rosenblatt, Industrial and Engineering Chemistry, vol. 35, no. 9, 1943). The present disclosure focuses on reactions among the distillate components, including possible reactions of distillate components and extracted wood-derived components and the unexpected results of a novel modification to the chemical milieu that affects the aging process.
Unaged spirits distillates are composed principally of varying amounts of ethanol, acetaldehyde, water, fatty acid esters and ethyl acetate. An average American whiskey (Bourbon) distillate contains about 12 g/100 PL (grams per 100 liters at 100xc2x0 proof) of ethyl acetate; and malt whiskey, such as that known as Scotch, as much as 29 g/100 PL of ethyl acetate.
During barrel-aging, the predominant transformation in the distillate in quantitative terms is the linear increase in ethyl acetate due to the oxidation of ethanol. Over the lengthy course of barrel-aging, ethyl acetate may increase from three to six times the amount originally present in the distillate (Reazin; American Journal of Enology and Viticulture; vol. 32, no. 4, 1981). In particular, during barrel-aging, ethyl acetate is formed initially from acetic acid already present in the distillate and according to industry investigators, perhaps additionally from acetic acid formed by degradation of the barrel wood. After this initial period, the formation of ethyl acetate is dependent upon the oxidation of ethanol into acetic acid at a uniform, linear rate.
Industry scientific investigators report the mechanism of ethanol transformation during barrel-aging as follows (Liebmann and Rosenblatt, 1943):
1. Ethanol+O2xe2x86x92acetaldehyde
2. Acetaldehyde+O2xe2x86x92acetic acid
3. Barrel wood - - - ↑
4. Ethanol+acetic acidxe2x86x92ethyl acetate+H2O
In conventional barrel-aging, the pH takes about 6 months to drop to the required acidic levels for the various reactions necessary for the development of beverage character to occur. Thereafter, the production of ethyl acetate is dependent upon the formation of acetic acid in the barrel, which takes 36 to 48 months to reach the level of marketable, aged beverages, often 4 years old (Reazin, 1981). It would be desirable in the distillery art to be able to accelerate this process, so that the same character of beverage could be produced in a much shorter time period. The present disclosure provides methods of aging beverages that result in distilled beverages that are aged for much shorter periods, even as short as about 30-40 days or even less, that have the character conventionally achieved only after four years of aging.
The present disclosure provides an improvement in the aging process of beverages that are normally aged in contact with a wood product such as an oak barrel or other wood product. The invention provides a means of aging a beverage in contact with a wood product, so that the beverage acquires the desired organoleptic characteristics that are associated with wood-aged beverages, in an accelerated manner. The present disclosure provides methods by which a raw distilled liquid may be contained in a closed system and circulated through a flavor transfer cartridge containing a comminuted wood product, thus acquiring the organoleptic character of a matured beverage in a greatly accelerated manner. It is a further aspect of the disclosure that through manipulation of the ethyl acetate levels prior to or during the flavor transfer process in certain beverages, one may further accelerate the aging process. The practice of the processes disclosed herein have allowed the present inventors to age a beverage to attain the characteristics of a conventional four year or longer aging process in just months, and in certain embodiments, in as little as about 15 to 40 days.
It is known in the art that contacting a raw beverage with wood, by storing the beverage in an oak barrel, for example, or by storing the beverage in contact with a prepared wood product allows the beverage to acquire a smooth character and more desirable taste due to extraction of certain compounds from the wood, and also due to the oxidation of certain alcohols and aldehydes. It is also known that certain beverages, including rum, whiskeys such as Bourbons, Scotches, ryes, and certain tequilas owe a large part of their flavor to the concentration of acetic acid in the final product. From looking at the reactions shown in the previous section, it can be seen that in the conventional maturation process, it is widely believed that ethanol is oxidized to acetic acid, and that this acetic acid then reacts with another portion of the ethanol to produce ethyl acetate and water, and that up to ⅔ of the final acetic acid is derived from those oxidation reactions (Reazin, 1981). It is a surprising discovery of the present inventors that, using the processes described herein, the majority of the acetic acid appears to be derived from the wood product. In the conventional aging process, a portion of this acetic acid reacts with ethanol to form ethyl acetate. An aspect of the present disclosure is a method of providing ethyl acetate in the raw beverage, thus xe2x80x9cdrivingxe2x80x9d the last step in the reactions shown above in the opposite direction, toward acetic acid. It is contemplated by the inventors, that this allows the beverage to attain higher levels of acetic acid and other desired esters in an accelerated reaction, thus contributing to the accelerated aging process described herein.
It is an aspect of the invention, therefore, that one of skill in the art may determine the level of acetic acid and ethyl acetate in the unaged beverage, and can then add an amount of ethyl acetate to the unaged beverage that is targeted to the final product. This amount may be determined by matching it to the amount found in a similar distillate after conventional aging, or it may be adjusted in order to obtain a beverage with a certain desired flavor or characteristic, such as an increase in fruity or pineapple flavor, for example. This predetermined or target ethyl acetate level that is necessary to achieve the desired final beverage composition may be adjusted by adding ethyl acetate to the raw distillate as described herein, and it may also, in certain embodiments, be added by the xe2x80x9cartxe2x80x9d of fermentation and distillation to achieve a higher ethyl acetate concentration in the raw distillate.
As discovered by the present inventors, it is typical that about 1 to 2 grams per 100 PL of ethyl acetate will be converted in the final equilibrium during the described aging processes, so that a sufficient amount of ethyl acetate must be added in order to account for that conversion. If, for example, a concentration of about 23 grams per 100 PL ethyl acetate is desired in the aged beverage, then the distillate would be adjusted to have about 23.5, 24 or up to about 26 grams per 100 PL when the aging begins. The amount of ethyl acetate in the mature beverage will depend on the type of beverage and the desired characteristic taste. In light of this knowledge, one of skill in the art could either add the desired amount of ethyl acetate to the raw distillate, or alter the fermentation and distillation conditions in order to achieve the same ethyl acetate level. Either method would, of course, fall within the scope of the disclosed invention.
The present invention may be described in certain aspects, therefore, as a method of maturing a beverage, the method including combining an unaged, or partially aged beverage, and a wood product, and processing said beverage in conditions effective to produce a mature beverage. The invention may also be described as a method of maturing a beverage that includes combining an unaged or partially aged beverage, ethyl acetate, and a wood product; and aging the beverage in conditions effective to produce a mature beverage and wherein the wood product is prepared by the process of comminuting raw, untreated wood into granules, heating the granules to a temperature of from about 100xc2x0 C. to about 240xc2x0 C. for a period of at least one hour, contacting the granules with a solution of aqueous ethanol containing from about 50% to about 95% ethanol at a temperature of up to about 55xc2x0 C., separating the granules from the solution, and heating the granules to a temperature of up to about 220xc2x0 C. for a period of at least about 15 minutes.
As described herein, a beverage to be aged according to the present disclosure may include any beverage that is aged in contact with wood and is preferably an ethanolic, or ethanol containing beverage, and is more preferably a brown distilled beverage. xe2x80x9cBrown distilled beveragexe2x80x9d or xe2x80x9cbrown distilled spiritxe2x80x9d is used interchangeably herein and is a term known in the art to mean beverages aged in contact with oak. Preferred embodiments include any type of whiskey, including, but not limited to American Bourbon, Scotch, Irish, rye, Canadian or other whiskey, rum, tequila, brandy, cognac, armagnac, liqueur, mescal, eau de vie, aguardiente, or shogu (shouchuu).
It is understood that the present invention may be practiced in combination with barrel aging of a beverage, to begin or finish a maturing process for a beverage that is partially aged in a barrel. In preferred embodiments, however, the raw distillate, or a partially aged distillate is aged in a liquid impermeable container, and/or a closed system that prevents a loss of water or ethanol, such as may occur when a beverage is aged in an oak barrel or cask. The system may be made of any suitable material, preferably a material that does not react with ethanol as do many metals, and the most preferred system would be made of stainless steel or glass. It is also an aspect of certain preferred embodiments that the aging process may take place at an elevated temperature in order to increase the reaction rates within the beverage. As such, preferred processing conditions may include a temperature of from about 70xc2x0 to about 170xc2x0 F., and more preferably from about 120 to about 170xc2x0 F., and even more preferably from about 140xc2x0 to about 150xc2x0 F. It is a further aspect of the preferred embodiment that air or oxygen is provided to the beverage during the aging process.
A wood product as used in the practice of the present invention may be any suitable wood product, and is preferably a charred wood product, and more preferably a comminuted, charred wood product, and more preferably a wood product produced by a process including comminuting raw, untreated wood into particles or granules; heating the granules to a temperature of from about 100xc2x0 C. to about 240xc2x0 C. for a period of at least one hour; contacting the granules with a solution of aqueous ethanol containing from about 20% to about 95% ethanol at a temperature of up to about 55xc2x0 C.; separating the granules from the solution; and heating the granules to a temperature of up to about 220xc2x0 C. for a period of at least about 15 minutes. A particularly preferred product is a wood product described in co-pending and commonly assigned U.S. patent application Ser. No. 09/449,927, incorporated herein by reference with respect to its description of such product, its characteristics, its method of manufacture, and its basic utility. The product so referenced is produced commercially as e.g., the Allegro(trademark) wood product produced and sold by Kairos Corporation.
The amount of ethyl acetate that is added or that is contained in the distillate prior to aging the beverage is somewhat flexible and is based on the amount of ethyl acetate in the raw beverage and the amount that is desirable in the finished, aged beverage. It is the experience of the present inventors, for example, that one may add enough ethyl acetate to the raw distillate to bring the concentration to a level that is somewhat higher than the desired concentration in the aged beverage. The target level may be based on a concentration found in a product that has been aged in a more conventional manner, whose organoleptic qualities one is trying to match, or a level may be based on a novel desired characteristic of the aged beverage.
In any case, it is contemplated that in the practice of the disclosed invention, one may add any desired level of ethyl acetate that is within the limits of a chemical equilibrium between the ethyl acetate, ethanol, and acetic acid as described herein above, and in certain embodiments would be from as little as a trace of ethyl acetate to from about 2 to about 100 grams per 100 PL of ethyl acetate, or from about 2 to about 30 grams per 100 PL of ethyl acetate inclusive, and including any particular number falling within those ranges. The number will vary, of course, depending on the beverage, and the desired characteristics of the finished or aged product.
An embodiment of the present invention may also be described as a method of maturing an ethanolic beverage to achieve a desired organoleptic character comprising combining a raw distillate; a wood product; and from about 2 to about 100 g/100 PL of ethyl acetate; and aging said beverage in conditions effective to produce a mature ethanolic beverage. An embodiment may also be described as an accelerated aging process for a distilled beverage, effective to produce a beverage with a character of flavor similar to a conventionally aged beverage comprising combining a raw distillate; a wood product; and from about 2 to about 100 g/100 PL of ethyl acetate; and storing said beverage in conditions effective to produce a mature ethanolic beverage. An embodiment may further be described as an accelerated aging process for producing an aged ethanolic beverage, the improvement comprising adding ethyl acetate to a distillate prior to the aging process.
The present invention may also be described in certain embodiments as a process for accelerating the maturation of an unaged or partially aged beverage comprising determining a target concentration of ethyl acetate for the product of the maturation; providing an unaged beverage with from about xc2xd to about 2xc2xd grams/100xc2x0 PL of ethyl acetate in excess of the target concentration; flowing the unaged beverage through a closed system wherein the closed system comprises a beverage aging wood product such that a beverage passing through the system contacts the wood product; and processing the beverage in the presence of oxygen for a period of time sufficient to produce a matured beverage. In certain embodiments, a closed system as described will include several containers in fluid connection through a series of pipes or piping and may include a distillate feed tank that may be connected to the output of a still, or that is the storage tank for an unaged beverage. This tank may be connected by piping or tubing to a pump that circulates the beverage through a heat exchanger, a filter and into a device that contains a wood product for aging, or transferring flavor to the beverage. As mentioned above, the distillate should not be in contact with materials that react with ethanol, and a preferred system is constructed of stainless steel.
In certain preferred embodiments, the wood product containing device is an interchangeable cartridge, preferably a stainless steel cartridge that is configured to be temporarily placed in the closed system for use in maturing a single batch or run of the unaged beverage. By interchangeable is also meant that one cartridge may used and then removed from the system without affecting any of the other components. Subsequently another cartridge may be added in its place for the next run. In this way, the system may be set up in a permanent location and used for the aging of many different beverages. A particular cartridge would then be designed for each individual beverage to be aged, and placed into the system for that particular run.
A cartridge includes a connection or port for introducing beverage from the system into the cartridge, includes an interior cavity for holding the wood product and for contacting the wood with the beverage while the beverage passes through the cartridge, and includes an outlet port for circulating the beverage from the cartridge back into the system. In the practice of the disclosed processes, then, one may prepare a cartridge with the amount of wood product necessary to achieve a particular flavor of mature beverage for a given amount of raw distillate. After use, the cartridge may be removed and another cartridge inserted into the system that contains wood product for the next run. In this way, the system provides flexibility in that a raw distillate of a beverage may be processed into a mature beverage with the character of a four year old conventional aging, for example, or it may be processed in the same system to achieve a beverage with a sixteen year old character, for example, by selecting the appropriate cartridge (with the appropriate wood product inside) and the appropriate ethyl acetate concentration in the unaged beverage. For example, a 4 year old rum sample may have less ethyl acetate and/or less acetic acid and other flavor producing esters than a 12 year old rum from the same distiller. Therefore, in order to obtain a mature rum with the 12 year old character, one would add more ethyl acetate to the raw distillate, and would include more wood product, and/or a wood product with flavor characteristics selected to achieve the character of the 12 year old rum.
In certain embodiments, the closed systems disclosed herein will include a pump for circulating the beverage in the system and will contain other elements including, but not limited to an inlet for injecting gas or air into the system, a heat exchanger configured to control the temperature of a beverage in the system, and a flush tank and piping configured to flush the residual beverage from the wood product cartridge after a processing run. This flush may then be used to dilute the mature beverage in those cases in which a lower proof product is desired. The system may also include a valve for sampling the beverage during processing to monitor the chemical or organoleptic properties of the beverage during processing.
An aspect of the present invention is also a matured beverage obtained by the processes disclosed herein. Such beverages may be bottled or packaged without further treatment or mixing, or they may be blended with other spirits or liquids including those of the same or similar type, or with a flavored beverage, such as a fruit flavoring. They may also be blended with a pure grain alcohol, for example, or diluted with water to achieve a desired proof.
A further aspect of the present invention is a beverage flavor transfer cartridge as described above, and configured to fluidly connect into a beverage maturation processing system, wherein the cartridge contains a beverage aging wood product in an amount effective to mature a predetermined amount of unaged, or partially aged beverage. In preferred embodiments the cartridge contains a wood product that is prepared by a process comprising comminuting raw, untreated wood into granules; heating the granules to a temperature of from about 100xc2x0 C. to about 240xc2x0 C. for a period of at least one hour; contacting the granules with a solution of aqueous ethanol containing from about 50% to about 95% ethanol at a temperature of up to about 55xc2x0 C.; separating the granules from the solution; and heating the granules to a temperature of up to about 220xc2x0 C. for a period of at least about 15 minutes.